Allium tuolumnense is a rare species of wild onion known by the common name Rawhide Hill onion. It is endemic to Tuolumne County, California, where it is known only from a small section of the Sierra Nevada foothills. It is a plant of serpentine soils. This onion grows from a reddish-brown bulb one to two centimeters long, producing a slender erect stem up to 50 centimeters tall and usually a single leaf approximately the same length. The stem is topped with a hemispheric flower cluster holding 20 to 60 flowers, each on a pedicel one or two centimeters long. Each flower is just under a centimeter wide when fully open, with six white or pink oval-shaped petals. There are six stamens and the ovary has six pointed crests.